I have problemabout fault reject rate at AOI very high, due to inspection letter or marking on IC body. It have uncleary. When I check at raw mat'l of IC it no problem but after pass reflow process it show marking not clear ( Laser marking type). Please advice how to solve this problem.

What is changing the marking on the part? * Is flux residue coating the part to change the the way light reflects from the part surface? [Run a board with tape on the part, then remove the tape prior to AOI] * Is the heat of the oven changing the marking? [Run a raw material part through the oven, the AOI the part]

Thank you for kindness advice. From the result of IC after pass the reflow process. The color of letter will change to similar color of material compound of IC. Then when we inspection by AOI machine, we have many problem about high fault reject rate at AOI cause from marking not sharp and color almost the same of IC body color. This part no have residue of flux. Normally IC marking will have some changing after pass reflow process. Per our suspect if we have problem about temp profile setting why some IC that same size or smaller than this part have a little changing at IC marking. Per investigate about the laser mark of IC if the color look like bright-brown then AOI machine can seperate percent bright lighting level of letter on IC and body of IC. But if IC have color dark brown or nearly same color of IC body. For our problem we loss a lot of time to reconfirm inspection at AOI machine to checking about marking to confirm no defect wrong part or orientation of IC. I want to know another SMT company face low yield of AOI cause IC marking unclear same us or not.

Every time to create new AOI program we must manual set at bright lighting level for each component. then this case we think the parameter of AOI setting it not concern for this problem due to the golden board that we use to confirm machine before start run assembly the same IC part no. The result of golden board testing is OK no fault reject at this part. But when we start to test mass production in PCBA that have this part, we still found fault reject at this IC.

So your golden board isn't a valid representation of your production material. I don't use AOI but it sounds like either you need a vendor that can guarantee the same part marking appearance as you originally programmed to (not likely) or you need a new golden board.

Our AOI machine can save various views of the same part number since we all know that different manufacturers will mark parts differently, some manufacturers vary their own marks. We get parts from the same manufacturer but different date codes that have different quality of print and or different fonts.